| Epoxidation of alkenes is one of the most important reactions in organic, synthesis. Transition metal complexes, and especially Salen Mn(â…¢) complexes have been proven to be very effective catalysts to catalyze this reaction. To design and synthesize novel manganese complexes and to prepare the immobilized traditional chiral Salen Mn complexes undoubtedly have the very important theoretic and realistic values. Therefore, it is very desirable to develop the designs and syntheses of novel non-salicylaldehyde Salen Mn complexes and PEG-immobilized chiral Salen Mn complexes with "Solvent-Controlled-Phase Transfer". The research works were as followings:(1) A series of novel non-salicylaldehyde based Salen ligands have been synthesized from the condensation of dialdehyde or diketone with o-aminophenol and the corresponding manganese (â…¢) complexes prepared by further coordination of them with Mn(OAc)2. 2H2O. FT-IR, UV-Vis spectra, chemical analysis and the structure optimized by Hartree-Fork/3-21G+ all indicated that the qualities of these novel Mn complexes were relative to their molecular structures. More specifically, glyoxal based Mn complex 2c being similar to the traditional Mn(â…¢)-salicylethylenediamine, had a short carbon chain and non geometrical constraint of the aliphatic bridge in the two o-aminophenol, and its quality was the best when compared to glutaraldehyde, 2,4-pentanedione and 1,3-cyclohexanedione based Salen Mn(â…¢) complexes (3c, 4c and 5c). And it was also the excellent catalyst for the epoxidations of several non-functionalized alkenes with molecular oxygen/sacrificial -isobutyaldehyde, PhI(OAc)2 or H2O2 as oxidant.(2) It has been firstly reported that a novel glucose based Salen Mn(â…¢) complex was synthesized via the condensation of glucose with 1,2-diaminobenzene and then the coordination with Mn(OAc)2. 2H2O. Such novel ligand and its Mn(â…¢) complex were characterized via FI-IR and UV-Vis spectra, as well as chemical analysis. The results indicated that this novel glucase based ligand could coordinate Manganese ions to form its Salen Mn(â…¢) complex. But the structure of the ligand optimized by the method of Hartree-Fork/3-21G+ with Gaussian 03 software and the Mn content measured by chemical analysis all supported that the ligand showed a weaker coordination capacity to Mn ions than the traditional Salen ligand, this is likely that a weak bonding capacity of the aliphatic hydroxyls and the geometrical constraint of large bulk ligand molecules influence its coordination towards Mn ions. In catalyzing the epoxidations of several un-functionalized alkenes with oxygen in the presence of isobutyraldehyde, this Mn complex showed the excellent catalytic performances for cyclohexene epoxidation, 100 % of conversion and 89 % of selectivity for epoxycyclohexane were obtained under the optimum reaction conditions. However, it showed slightly low activity and selectivity as well as poor ee values in catalyzing the epoxidations of styrene and E-stillbenzene.(3) PEG-400 and PEG-800 immobilized chiral Salen Mn(â…¢) complexes have been successfully prepared through the chemical grafting and axial coordinating approaches, and characterized by FT-IR, UV-Vis, GPC, chemical analysis. The asymmetric epoxidation of styrene was employed to check the catalytic performances of these immobilized catalysts. The results indicated that NaClO, PhI(OAc)2 can be used as oxidants in the epoxydation of styrene. The grafted catalysts have similar catalytic properties and slightly higher ee's value when compared with traditional homogeneous Salen Mn(â…¢) catalyst. Most importantly, the grafted catalysts possessed a character of "Solvent regulated phase-transfer", namely, they were soluble in dichloromethane medium during the reaction. After the reaction, they could be precipitated and recycled from the reaction system via adding no-polarity solvent (n-hexane). For example, the catalyst could be recycled for 3 times when PhI(OAc)2 were used as an oxidant. However, the recycled results were not satisfied in the presence of basic hypochlorite solution (pH=11.3) due to the fact that the strong oxidation and especially the basicity of hypochlorite could destroy the Mn catalysts. This could be confirmed from the fact that the recycled efficiency of the catalyst was slightly improved by decreasing the basicity of hypochlorite solution (pH=9.3).
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